Relationship between medial meniscus extrusion and osteophyte formation in early-stage knee osteoarthritis: an ultrasound-based multicenter cross-sectional study.

PURPOSE: Medial meniscus extrusion compromises the ability of meniscus to distribute a load across the knee joint and is recognized as a risk factor for knee osteoarthritis. Despite a positive correlation between medial meniscus extrusion and medial tibial osteophyte width, the sequence of these pathological changes remains unclear. In this multicenter cross-sectional study, we aimed to clarify the relationship between osteophyte formation and medial meniscus extrusion by comparing extrusion distances in knees with and without medial tibial osteophytes.

METHODS

We enrolled 207 Japanese patients with early-stage knee osteoarthritis, defined as Kellgren-Lawrence grade ≤ 2. Participants underwent radiography, magnetic resonance imaging, and ultrasonography (US). Knees were categorized into three groups based on the presence of osteophytes: N (no osteophytes), U (osteophytes detected only with US), and O (osteophytes detected with both radiography and US). The medial meniscus extrusion distance was assessed using US.

RESULTS

Among the 211 knees evaluated, 89 were classified into the N group, 93 into the U group, and 29 into the O group. The medial meniscus extrusion distance was significantly greater in the O group (3.3 ± 1.3 mm) than in both the N (2.3 ± 1.1 mm, p < 0.001) and U (2.6 ± 0.9 mm, p = 0.004) groups. No significant difference was detected between the N and U groups (p = 0.27).

CONCLUSION

Medial meniscus extrusion was significantly associated with osteophyte formation in early-stage knee osteoarthritis.